Two-layer coating system, ceramic powder and a layer

Abstract

The invention relates to a coating system (1), comprising at least a metallic substrate (4), optionally a metallic bond coat layer (7) on the substrate (4), and a ceramic sub-layer (10) of tetragonal zirconia, comprising 3.5 wt% to 8.0 wt% yttrium oxide and 6.0 wt% to 8.0 wt% ytterbium oxide, and a ceramic top layer (13) of cubic zirconia on the ceramic sublayer (10).

Description

[0001]2023PF12477 1 Description Two-layer coating system, ceramic powder and a layer The invention relates to a two-layer coating system, ceramic powder and a layer. Ceramics generally exhibit very good stability at high temperatures and are therefore often used as ceramic coatings on high-temperature components, such as turbines, especially gas turbines. An important aspect of this type of application is the bonding of the ceramic coating to a substrate, which often consists of a metallic substrate. Known are metallic bond coat layers, such as those based on NiCoCrAlY, as well as ceramic bonding layers, resulting in a two-layer ceramic coating system. Therefore, the aim is to improve the thermal insulation properties of the ceramic coating systems. It is therefore the object of the invention to solve the above-mentioned problem. The object is achieved by a coating system according to claim 1, a powder according to claim 6, and a layer according to claim 7. Further advantageous measures are listed in the dependent claims, which can be combined arbitrarily with each other to achieve additional advantages. Ceramic coatings based on stabilized zirconia are known, with fully stabilized zirconia (FSZ) often being used due to its better thermal stability. However, the aim of the idea is to use partially stabilized zirconia and fully stabilized zirconia with improved thermal stability. The figure schematically shows an exemplary embodiment of the invention. 2023PF12477 2 The figure and the description only represent exemplary embodiments of the invention. In a coating system 1, a ceramic sub-layer 10 is applied to metal, with a metallic bond layer 7 preferably being present when nickel- or cobalt-based superalloys are used as substrate 4. The metallic bond coat layer 7 preferably comprises an aluminide, platinum aluminide, or is based on a NiCoCrAlY-X alloy, optionally with X = Ta, Re, Fe, and / or Si, forming aluminum oxide (TGO, not shown). The ceramic top layer 13 on the ceramic material according to the invention can be produced by plasma spraying (APS, ...), HVOF, EB-PVD, SPPS, and preferably reveals a columnar or segmented structure. The ceramic top layer 13 preferably has a thickness of 100μm to 1000μm. Similarly, the ceramic sub-layer 10 is present, but its thickness is at least 20% thinner than that of the ceramic top layer 13. All following values are in wt%. The ceramic sub-layer 10 comprises partially stabilized zirconia. The partially stabilized zirconia of the ceramic sub-layer 10 is stabilized with 3.5% to 8.0%, especially with 4.0% to 6.5%, base stabilizer yttrium oxide (Y2O3) as well as with 6.0% to 8.0% ytterbium oxide (Yb2O3) and optionally hafnium oxide / aluminum oxide. The ceramic material preferably contains 3.0% to 4.0% yttrium oxide (Y2O3), preferably 6.5% to 7.5% ytterbium oxide (Yb2O3), and also preferably optional: hafnium oxide (HfO2) with 0.2% to 4.0%, especially 0.5% to 2.5% hafnium oxide (HfO2). On the ceramic sub-layer 10, the ceramic top layer 13 with a cubic structure of zirconia is applied. 2023PF12477 3 The cubic zirconia for the ceramic top layer 13 preferably contains yttrium oxide-stabilized zirconia, with the proportion of yttrium oxide being 18.0% to 22.0%, especially 20.0%. It is also possible to use a cubic zirconia for the ceramic top layer 13 with stabilizers of yttrium oxide, ytterbium oxide, and gadolinium oxide. Preferably, the following proportions are then used: 8.5% - 11.5% yttrium oxide, 4.0% - 7.0% ytterbium oxide, and 3.5% - 6.5% gadolinium oxide, most preferably 9.0% - 11.0% yttrium oxide, 4.5% - 6.5% ytterbium oxide, and 4.0% - 6.0% gadolinium oxide. Best results are archived by 9.5% - 10.0% yttrium oxide, 5.2% - 6.0% ytterbium oxide, and 4.8% - 5.6% gadolinium oxide. Accordingly, a powder for this cubic zirconia is used, which comprises at least: 8.5% - 11.5% yttrium oxide, 4.0% - 7.0% ytterbium oxide, and 3.5% - 6.5% gadolinium oxide, preferably 9.0% - 11.0% yttrium oxide, 4.5% - 6.5% ytterbium oxide, and 4.0% - 6.0% gadolinium oxide. The powder may contain polymers for forming pores during coating, binders for spraying or slip-casting, or binder-jet printing, or abrasive particles (non-zirconium oxides, especially BN, ZrC, etc.). Examples of a ceramic sub-layers 10: • 3.6% Y2O3 / 6.5% Yb2O - ZrO2 • 3.4% Y2O3 / 6.7% Yb2O / 0.5% Al2O3 - ZrO2 • 3.6% Y2O3 / 6.5% Yb2O / 1.2% HfO2 - ZrO2 • 3.5% Y2O3 / 6.4% Yb2O / 1.1% HfO2 / 0.3% Al2O3 - ZrO2; Examples for the ceramic top layer 13, which can be used in combination with the examples of the ceramic sub-layer 10: 2023PF12477 4 • 20% Y2O3 - ZrO2 • 10.0% Y2O3 / 5.5% Yb2O3 / 5.3% Gd2O3 - ZrO2.

Claims

2023PF12477 5 Patent claims 1. Coating system (1), comprising at least a metallic substrate (4), optionally a metallic bond coat layer (7) on the metallic substrate (4), and a ceramic sub-layer (10) of tetragonal zirconia, comprising 3.5 wt% to 8.0 wt% yttrium oxide, especially 4.0 wt% to 6.5 wt% yttrium oxide, and 6.0 wt% to 8.0 wt% ytterbium oxide, as well as optional hafnium oxide and / or aluminum oxide, and a ceramic top layer (13) of cubic zirconia on the ceramic sub-layer (10).

2. Coating system according to claim 1, wherein the ceramic top layer (13) contains yttrium oxide-stabilized zirconia, with the proportion of yttrium oxide being 18.0 wt% to 22.0 wt%, especially 20.0 wt%, particularly only containing yttrium oxide.

3. Coating system according to claim 1, wherein the ceramic top layer (13) comprises zirconia, with stabilizers of yttrium oxide, ytterbium oxide, and gadolinium oxide, with the following proportions preferably present: 8.5% - 11.5% yttrium oxide, 4.0% - 7.0% ytterbium oxide, and 3.5% - 6.5% gadolinium oxide, preferably 9.0% - 11.0% yttrium oxide, 4.5% - 6.5% ytterbium oxide, and 4.0% - 6.0% gadolinium oxide. particularly preferred are: 9.5% - 10.0% yttrium oxide, 5.2% to 6.0% ytterbium oxide, and2023PF12477 6 4.8% - 5.6% gadolinium oxide.

4. Coating system according to one or more of claims 1, 2, or 3, comprising a metallic bond coat layer (7) between the ceramic layers (13, 10) and the metallic substrate (4), especially directly on the metallic substrate (4), wherein the bond coat layer (7) comprises an alloy of the type NiCoCrAlY—X, where X is optionally = Ta, Re, and / or Si, especially NiCoCrAlY or NiCoCrAlY-Ta.

5. Coating system according to one or more of claims 1, 2, 3 or 4, wherein the ceramic sub-layer (10) is at least 20% thinner than the ceramic top layer (13).

6. Powder for a ceramic layer, comprising at least: 8.5% - 11.5% yttrium oxide, 4.0% - 7.0% ytterbium oxide, and 3.5% - 6.5% gadolinium oxide, preferably 9.0% - 11.0% yttrium oxide, 4.5% to 6.5% ytterbium oxide, and 4.0% - 6.0% gadolinium oxide, more preferably 9.5% - 10.0% yttrium oxide, 5.2% to 6.0% ytterbium oxide, and 4.8% - 5.6% gadolinium oxide.

7. Layer comprising a composition according to claim 6 or produced from a powder according to claim 6.

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